The present invention relates to a surveying system for projecting a laser beam in rotary irradiation to form a laser reference plane and for measuring a position based on the laser reference plane.
As a device for forming a reference plane in wide range, a rotary laser irradiation device is known, which projects a laser beam in rotary irradiation. Also, a surveying system is known, in which a photodetection unit is mounted on a working machine such as a bulldozer and other machines and which is used to carry out civil engineering work such as ground leveling operation and other operations according to the detection of the laser reference plane by the photodetection unit.
As one of such types of the rotary laser irradiation devices, a device is known, which projects a plurality of fan-shaped laser beams with at least one of the fan-shaped laser beams tilted at a known angle in rotary irradiation. This type of rotary laser irradiation device can receive and detect the laser beams and can measure an elevation angle and an elevation (high-low) position with the rotary laser irradiation device as a reference based on difference of photodetection time of a plurality of the fan-shaped beams.
When a rotary laser irradiation device is installed and a photodetection unit is mounted on the working machine and civil engineering work is carried out according to the laser reference plane, the working operation generally lasts for a long time, i.e. from the morning till the evening in most cases. Also, there may be extreme temperature change, and the rotary laser irradiation device is subjected to the influence of temperature change. For instance, a rotation shaft of rotary mechanism may be titled due to temperature change, and the projecting direction of the laser beam may change. Or, the posture of the installation of the rotary laser irradiation device may change by vibration or the like. Such change may appear as a positional change over time of the laser reference plane formed by the device, and the laser reference plane, which should be in horizontal direction, may have a tilting component. When the laser reference plane is tilted or the laser reference plane is subject to positional change, error may occur in the civil engineering work, which is carried out by using the laser reference plane as a reference.
It has been practiced in the past that, if the errors over time of the laser reference plane is not allowable, inspection measurement is performed at a certain predetermined time interval during the operation time in one day, and the result of the measurement is compensated or the laser reference plane is re-set each time to maintain the operation accuracy.
When the result of measurement is to be compensated, the procedure is complicated. When the laser reference plane is re-set, an operator must go back to the rotary laser irradiation device and must perform the re-setting procedure, and this makes the operation more complicated and troublesome. Also, the errors caused prior to the moment of re-setting cannot be compensated. Further, the operation must be interrupted during the re-setting procedure, and this causes difficulties and inconveniences, which result in lower working efficiency.
A rotary laser irradiation device for projecting a plurality of fan-shaped laser beams with at least one of the fan-shaped laser beams tilted at a known angle and a surveying system using this type of rotary laser irradiation device are disclosed in JP-A-2004-212058 and JP-A-2005-274229.